Mechanical motion control apparatus

ABSTRACT

There is disclosed herein a mechanical motion control mechanism which in one form may comprise an input shaft drivingly connected to an output shaft in such a manner that continuous rotation of the input shaft produces varying rotational movement of the output shaft characterized by an initial dwell period, an acceleration period, a constant velocity period, a deceleration period and another dwell period. The input and output shafts may be drivingly connected by means of a gear secured to the input shaft which is in meshing engagement with a second gear supported at one end of a pivot arm, the other end of which is secured to the output shaft. Rotational and revolving movement of this second gear is controlled by the interaction of a plurality of cam followers engaging a cam surface so as to allow rotational, revolving, and various desired combinations of such movements in response to rotational movement of the first gear. Alternatively, the input and output shafts may be drivingly connected by sprockets in place of the first and second gears with an interconnecting drive chain, belt or other similar devices. Also, if desired, the first and second gears may be replaced with wheels having circumferential frictional surfaces in mutual driving engagement. In yet another embodiment the input and/or output may be in the form of linear motion in which case the first gear may be replaced with a rack engaging the second gear in such a manner as to produce the above movement period sequence.

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates generally to motion control mechanisms andmore particularly to such motion control mechanisms as are designed toprovide respective periods of dwell, acceleration and constant velocity.

The use of gears and shafts to transmit rotational forces which maythereafter be converted to linear motion is well known, the same beingemployed in various arrangements of work transfer machinery. In certainapplications this linear motion is reciprocal in nature employing areversible electric motor or transmission to effect movement in oppositedirections. Accordingly, mechanisms must be provided to shut off ordisconnect the driving means from the member being moved so as toproperly position same within a machine preparatory to an operationbeing performed on a workpiece. As any such movement cannot be stoppedinstantaneously, it is necessary to provide a deceleration period aswell as being desirable to also provide a dwell period during whichrotation of an input shaft will produce no rotation of an output shaftso as to enable maximum transfer speed and insure accuracy ofpositioning.

Accordingly, the present invention provides a mechanical motion controlmechanism which provides a dwell period, acceleration period, constantvelocity period, deceleration period and dwell period the relativelengths of which may be varied by alteration of the shape of the camsurface. In one form, the present invention employs a first gear,sprocket or wheel secured to a rotating input shaft which meshinglyengages or is otherwise drivingly coupled to a second gear, sprocket orwheel supported on one end of a pivot arm the other end of which isconnected to the output shaft. Cam followers are secured to the secondgear and engage a stationary cam surface so as to control rotational andcurvilinear movement of the second gear. In another embodiment a rack orthe like is provided which is drivingly coupled to a gear, sprocket orwheel associated with output means upon which suitable cam followers aresecured which cam followers engage a cam surface so as to controlrotational and linear motion of the output means thereby providingcontrolled periods of dwell, acceleration, constant velocity,deceleration and dwell. Thus, the present invention provides amechanical mechanism having a minimum number of moving parts which iscapable of transmitting high torques thereby being operative to movemassive articles which also provides a dwell period of sufficientduration to allow the drive means to be stopped without encounteringovertravel. The present invention therefore greatly facilitates thetransfer and positioning of articles such as workpieces within amachine.

Additional advantages and features of the present invention will becomeapparent from the subsequent description and the appended claims takenin conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front elevational view of the present invention showing theinput shaft in section;

FIG. 2 is a transverse sectional view of the present invention, thesection being taken along line 2--2 of FIG. 1;

FIG. 3 is a back elevational view of the present invention;

FIG. 4 is a graphical illustration of input shaft and output shaftvelocities versus time for one embodiment of the present invention;

FIG. 5 is an elevational view similar to that of FIG. 1 but with the camfollower illustrated in a dwell position;

FIG. 6 is a view similar to that of FIG. 5 but illustrating the camfollower in a position of accelerating output shaft movement;

FIG. 7 is a view similar to that of FIG. 5 but illustrating analternative drive coupling between the input and output shafts;

FIG. 8 is also a view similar to that of FIG. 5 but illustrating yetanother drive coupling between input and output shafts;

FIG. 9 is a fragmentary side elevational view of yet another embodimentof the present invention; and

FIG. 10 is a fragmentary side elevational view similar to that of FIG. 9but illustrating an alternative drive arrangement therefor.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to FIGS. 1 through 3, there is illustrated therein amechanical motion control apparatus indicated generally at 10 inaccordance with the present invention. The mechanical motion controlapparatus 10 comprises an input shaft 12 which is rotatably journaled ina support member 14 secured to a lower base member 16. A gear 18 issecured to one end 20 of the input shaft and is adapted to be rotatedthereby. A second gear 22 is disposed in meshing engagement therewith,the second gear being supported on a shaft 24 which is journaled in oneend 26 of an output shaft pivot arm 28, the other end 30 of which isfixedly secured and adapted to rotate with an output shaft 32. Thus,shaft 24 is supported in radial spaced relationship to output shaft 32which is substantially coaxial with the input shaft and is similarlyrotatably journaled in another portion of shaft support member 14. Shaftsupport member 14 is fixedly secured to a base member 16 which may forma portion of the transfer apparatus or other machinery for which themechanical motion control mechanism 10 is adapted to be utilized.

Secured to the front face 34 of the second gear member is a cam followersupport arm 36 which projects diametrically outward from opposite sidesof the second gear member. First and second cam follower members 38 and40 are secured to the outer ends of cam follower support arm 36 and arein the form of rollers adapted to follow along selective portions of acam surface.

A front panel member 42 is also provided which has a curvilinearinwardly facing edge surface 44 machined thereon which provides the camsurface to be engaged by one or both of the cam follower members 38 and40 provided on the cam support arm 36 secured to gear member 22. Camsurface 44 may be divided into five portions comprising a first dwellperiod 46, a first acceleration/deceleration period 48, a constantvelocity period 50, a second acceleration/deceleration period 52, and asecond dwell period 54.

Secured to the opposite end of shaft 24 supported in the output shaftpivot arm 28 is a secondary cam follower support arm 56 which hasdisposed at its opposite end a cam follower 58 similar to cam followers38 and 40 provided on the cam follower support arm 36. Cam follower 58is adapted to engage camming surfaces 60 and 62 provided on a rearsurface member 64 during dwell periods or possibly end portions ofacceleration/deceleration movement so as to provide a stabilizing effectto insure proper positioning of a workpiece being transferred by themotion control apparatus thereby assuring precise locating of the memberbeing moved. In order to support the front and back panel members 42 and64 which provide the camming surfaces, a pair of side members 68 and 70are provided extending therebetween and generally perpendicular to theparallel planes of the front and back pieces.

Both dwell portions 46 and 54 as well as constant velocity portion 50have constant radii of curvatures, the radius for the two dwell periodsbeing equal. Also, the center of curvature of the constant velocityportion is necessarily coaxial with the axis of rotation of input shaft12.

Referring now to FIGS. 3 through 6, the operation of the mechanicalmotion control mechanism of the present invention will now be explainedin detail. We will assume for the purposes of explanation that themechanical motion control apparatus is in a dwell position such as isillustrated in FIG. 5 with cam follower 38 engaging dwell portion 54 ofcamming surface 44. At time T₁ a driving means which is drivinglyconnected to input shaft 12 is turned on so as to cause acceleratingrotational movement of input shaft 12 thereby causing rotationalmovement of gear member 18. During the period of time T₁ to time T₂ therotation of the gear member 18 will impart rotational movement to gearmember 22 as the rotational axis 72 of gear member 22 is positioned atthe center of curvature of dwell portion 54. Also, cam follower 40 doesnot engage any surface during this period. Thus, both cam followers 38and 40 are allowed to move freely in rotational movement along with gearmember 22 providing a dwell period 73 during which output shaft 32remains stationary. At time T₂ cam follower 38 entersacceleration/deceleration portion 52 of camming surface 44 at which timerotational movement of gear member 22 is caused to decrease and begradually replaced by curvilinear or revolving motion of gear 22 withrespect to output shaft 32. This acceleration period 74 will continueuntil time T₃ at which time cam follower 40 will have rotated intoengagement with the constant velocity portion 50 of the camming surface44. Thus, at time T₃ both cam followers 38 and 40 will be in engagementwith spaced portions of the camming surface 44 thereby totallypreventing rotational movement of gear member 22 in response to therotational movement of gear member 18 and thereby forcing curvilinearmotion of gear 22 as the gear member 18 is continued to be rotated. Thisconstant velocity period 76 will continue until time T₄ at which timethe leading cam follower member 40 will enter the deceleration portion48 of the camming surface 44. During the period 78 from time T₄ to timeT₅ the leading cam follower 40 will be moving into the decelerationportion 48 of the cam surface and the trailing cam follower 38 will bemoving out of engagement with the camming surface 44 and beginning torotate about the axis of rotation 72 of the gear member 22. As the inputshaft continues to rotate gear member 18, the leading cam followermember 40 will move from the deceleration portion 48 into the dwellportion 46 during which time the movement of gear member 22 will becomepurely rotational in nature. This dwell period 80 will provide asufficient time T₅ to time T₆ during which the driving force beingapplied to the input shaft 12 may be disengaged or turned off withoutconcern as to overdriving or inaccurately positioning a workpiece beingtransferred by the mechanical motion control mechanism.

As is apparent gear 22, being rotatably supported in a pivot arm andhaving an axis of rotation spaced from the axis of rotation of theoutput shaft, rotational movement of gear member 22 will impart nomotion whatsoever to output shaft 32. Thus, during the periods of dwell73 and 80 there will be no movement of the output shaft even though gearmember 22 is rotating in response to rotation of gear member 18 securedto the input shaft 12. However, during periods of accelerationrespective of cam followers 38 and 40 will cause the rotational movementof gear member 22 to decrease and supplement such decreasing rotationalmovement with curvilinear movement thereby causing pivot arm 28 toimpart a rotational movement to output shaft 32. Once the constantvelocity portion 50 of the camming surface 44 has been entered, therewill be no rotational movement of gear member 22 but rather all suchrotational movement will be supplanted with pure curvilinear motionthereby causing pivot arm 28 to rotate through an arc of approximately180° as illustrated until such time as a leading cam follower 38 or 40,depending on the direction of movement enters the deceleration portion48 or 52 of the camming surface 44.

Referring specifically to FIG. 3, it will be seen that as cam followers38 or 40 enter their respective acceleration/deceleration portions 52and 48, cam follower support arm 56 will be caused to begin rotation dueto the increasing rotational movement of gear 22. As either cam follower38 or 40 moves into respective of dwell portions 54 and 46, cam follower58 will move into engagement with either cam surface 60 or 62respectively thereby acting as a stabilizer to insure proper positioningof a workpiece to be thus transported. During the constant velocityportion of movement, cam follower support arm 56 will be longitudinallyaligned with pivot arm 28. It should be noted that while cam followersupport arm 56, associated cam follower 58 and cam surfaces 60 and 62provide a steadying function, they may be omitted should this be desiredfor particular applications.

It should also be noted that the specific shape and contour of cammingsurface 44 may be varied to provide a wide variety of dwell periods,acceleration/deceleration, and/or constant velocity periods. Forexample, providing a longer acceleration/deceleration portion may beaccomplished by lengthening portions 48 and 52 whereas greater or lesserdwell periods can be provided by increasing or decreasing the length ofportions 46 and/or 52. The relative size of gears 18 and 22 will alsoaffect the duration of dwell and acceleration/deceleration periods aswell; that is to say, the greater the ratio of the diameter of gear 18to gear 22, the shorter the dwell and acceleration periods.

Referring now to FIG. 7, there is illustrated another embodiment of thepresent invention indicated generally at 82 which is substantiallyidentical to the embodiment of FIGS. 1 through 3, 5 and 6 describedabove with the exception of the driving connection between the input andoutput shaft. Accordingly, corresponding portions thereof are indicatedby identical numbers primed. In this embodiment, gears 18 and 22 arereplaced by sprockets 84 and 86 respectively, and a drive chain 88 isprovided extending around portions of the circumference and between eachof sprockets 84 and 86 so as to drivingly couple them together. Theoperation and motion produced will be substantially identical as thatdescribed above and therefore will not be described in detail. It shouldbe noted, however, that while apparatus 82 employs a chain 88 andsprockets 84 and 86, any other suitable drive arrangement may be easilysubstituted therefor such as for example a pair of V-belt sheaves and aninterconnecting V-belt.

Further, as illustrated in FIG. 8, another embodiment of the presentinvention is indicated generally at 90 which also is substantiallyidentical to the embodiments described above and thus correspondingportions are indicated by like numerals double primed. However, in thisembodiment, gears 18 and 22 are replaced by wheels 92 and 94 which areeach provided with circumferential surfaces 96 and 98 respectively whichprovide a high coefficient of friction. For example, a circumferentialsurface coating or belt may be provided which has a high coefficient offriction and may be easily replaced when worn. In this embodimentcircumferential surfaces 96 and 98 of wheels 92 and 94 respectively arein mutual frictional engagement so as to thereby transmit rotationalforces between the input and output shafts.

The present invention may also be easily adapted to provide sequentialdwell periods, acceleration periods, constant velocity periods,deceleration periods, and dwell periods with both linear input andoutput motions. Such an embodiment is illustrated and will be describedwith reference to FIG. 9.

Motion control apparatus 100 comprises a linear motion input drive meanssuch as piston 102 having piston rod 104 extending outward therefrom andadapted to reciprocate longitudinally. The outer end 106 of piston rod104 is connected to an input carriage assembly indicated generally at108 upon which a rack 110 of suitable length and having upwardly facinglongitudinally extending teeth 112 is secured. An output gear 114 havingteeth 116 is mounted in meshing engagement with teeth 112 of rack 110and has a cam follower support arm 118 fixedly secured to a side surface119 thereof. Output gear 114 may be rotatably supported or mounted uponany desired output means (not shown) such as a carriage assembly or thelike which is desired to be longitudinally reciprocated and which may bedesigned to carry a workpiece thereon.

Cam follower support arm 118 is generally T-shaped having outwardlyprojecting legs 120, 122 and 124 each of which is provided with camfollowers 126, 128, and 130 respectively secured to the outer endsthereof.

A cam surface 132 is provided having a relatively straightlongitudinally extending surface portion 134 which is adapted to beengaged by cam followers 126 and 128 so as to provide constant velocitymotion. Arcuate shaped surface portions 136 and 138 are provided atopposite ends of straight surface portion 134 and merge smoothlytherewith. Portions 136 and 138 are each adapted to engage cam followers126 and 128 respectively so as to provide accelerating or deceleratingmotion depending upon the direction of movement of carriage assembly108. Additional arcuate portions 140 and 142 merge smoothly with andextend from respective arcuate portions 136 and 138 and are adapted toengage corresponding cam followers 126 or 128 so as to provide dwellperiods. Arcuate portions 140 and 142 are both of a constant radius ofcurvature the radius being substantially equal to the distance betweenthe axis of rotation of gear 114 and respective cam followers 126 and128.

As illustrated in FIG. 9, leg portion 124 of cam follower support arm118 may be slighty longer than legs 120 and 122 and is provided with camfollower 130 which operates in a similar manner to that described abovewith reference to cam follower 58 to provide a steadying function duringthe dwell period. Accordingly, constant radius of curvature cammingsurfaces 144 and 146 are provided spaced slightly outward fromrespective surfaces 136, 140 and 138, 142.

The operation of motion control apparatus 100 is very similar to thatdescribed above with reference to apparatus 10. Let us assume thatcarriage assembly 108 is in the dwell position illustrated in phantom inFIG. 9 and about to begin movement to the left as seen therein. Duringthe dwell period, that being the time during which cam follower 128engages camming surface portion 142, gear 114 will be in pure rotationalmovement without any linear motion thereby allowing movement of pistonrod 104 and rack 110 to the left. As cam follower 128 moves into arcuatecamming surface portion 138, the pure rotational movement of gear 114will decrease being supplanted by increasing or accelerating linearmotion toward the left. When cam follower 126 moves into engagement withstraight camming surface portion 134, all rotational movement of gear114 will have ceased thereby preventing any further relative movement ofrack 110 and gear 114 and thus producing a period of constant linearvelocity toward the left due to the continued retracting of piston rod104. As cam follower 126 moves into arcuate camming surface portion 136,the pure linear motion of gear 114 will be caused to decrease ordecelerate being supplanted by rotational movement of gear 114 which inturn allows continued linear motion of rack 110. As cam follower 126moves into camming surface portion 140, all linear motion of gear 114will cease and be totally supplanted by rotational movement with camfollower 130 moving into camming surface portion 144 so as to insureprecise accurate positioning of a workpiece being moved thereby.

As previously mentioned, the relative lengths of the camming surfaceportions may be varied to provide any desired combination of perioddurations. Further, varying the diameter of gear 114 will also allowvariances in the rate of acceleration/deceleration and length of dwellperiods for a given rate of travel of rack 110. It should be noted, thelength or rack 110 must be sufficient to insure continuous engagementwith gear 114 throughout the periods of rotational movement of gear 114which requires rack 100 to be equal to twice the length of the arcthrough which gear 114 rotates during a single deceleration/accelerationdwell period.

While motion control apparatus 100 is illustrated employing a pistoninput drive arrangement, it should be noted that other linear drivearrangements may be easily substituted therefor. As illustrated in FIG.10, a lead screw drive arrangement may be substituted therefor in whicha rotating drive means 148 is drivingly connected to an elongated leadscrew 150 which extends through and threadedly engages a cylindricalmember 152 secured to input carriage assembly 108'. Thus rotation oflead screw 150 will cause longitudinal motion of carriage assembly insubstantially the same manner as with piston 102.

Thus, as is apparent the present invention provides a relatively simplemechanical motion control mechanism which provides beginning and endingdwell periods during which a driving force connected to the input shaftmay be either shut down or otherwise disconnected therefrom without lossof proper positioning of the workpiece being moved thereby. Further, themechanism of the present invention requires relatively few moving partsthereby increasing a reliability thereof while maintaining extremeflexibility in that the arc periods defining dwell portions as well asthe length of the acceleration periods and constant velocity periods maybe easily varied to provide any desired combination of dwellacceleration/deceleration and constant velocity periods during themotion. Thus, the mechanical motion control mechanism of the presentinvention is uniquely adapted for transferring or otherwise movingarticles into and out of machining apparatus or the like withoutsubjecting the article being so moved to any jarring acceleration ordeceleration forces as well as insuring that the articles are properlypositioned in a desired location.

While it will be apparent that the preferred embodiments of theinvention disclosed are well calculated to provide the advantages andfeatures above stated, it will be appreciated that the invention issusceptible to modification, variation and change without departing fromthe proper scope or fair meaning of the subjoined claims.

I claim:
 1. Mechanical motion control apparatus comprising:drive means including an input shaft and a first gear fixedly secured to said input shaft; driven means including an output shaft disposed coaxially with said input shaft and a second gear rotatably supported upon another shaft in meshing engagement with said first gear, said output shaft being rotatably driven by said second gear; movement control means connected to said driven means, said movement control means including a cam surface and an associated cam follower means, said cam surface and cam follower cooperating to provide a period of pure rotational movement of said driven means, a period of decelerating rotational and simultaneous accelerating revolving movement of said driven means and a period of constant velocity revolving movement of said driven means relative to said drive means while said drive means continuously moves at a substantially constant velocity.
 2. Mechanical motion control apparatus as set forth in claim 1 wherein said another shaft is radially spaced from said output shaft.
 3. Mechanical motion control apparatus as set forth in claim 2 wherein said another shaft is secured to one end of a pivot arm, said pivot arm having another end secured to said output shaft.
 4. Mechanical motion control apparatus as set forth in claim 1 wherein said second gear is operatively connected to and radially spaced from said output shaft, said movement control means and said drive means cooperating to selectively impart rotational movement to said output shaft through said second gear.
 5. Mechanical motion control apparatus as set forth in claim 4 wherein said output shaft is stationary during said period of rotational movement of said movement control means and is accelerating during said period of decelerating rotational movement.
 6. Mechanical motion control apparatus comprising:drive means; driven means driven by said drive means; and movement control means secured to said driven means, said movement control means including an elongated cam follower secured to said driven means, and a cam surface at least partially surrounding said drive and driven means, said cam surface cooperating with said cam follower to control movement of said driven means, so as to provide a period of pure rotational movement of said driven means, a period of decelerating rotational and simultaneous accelerating nonrotational movement of said driven means and a period of constant velocity nonrotational movement of said driven means relative to said drive means while said drive means continuously moves at a substantially constant velocity, said cam surface including a first portion comprising a slot having a constant radius of curvature for controlling said pure rotational movement, a second portion for controlling said decelerating rotational motion and a third portion for controlling said nonrotational motion, said third portion being of a constant radius of curvature having a center coaxial with the axis of rotation of said drive means.
 7. Mechanical motion control apparatus as set forth in claim 6 wherein said drive means includes an input shaft, a first gear fixedly secured to said input shaft and said nonrotational movement is revolving movement.
 8. Mechanical motion control apparatus as set forth in claim 7 wherein said driven means comprises a second gear rotatably supported upon a second shaft in meshing engagement with said first gear.
 9. Mechanical motion control apparatus comprising:supporting means; an input shaft journaled in said supporting means; an output shaft journaled in said supporting means coaxial with and spaced from said input shaft; a drive gear fixedly secured to said input shaft; a pivot arm having one end secured to said output shaft; driven gear means journaled on said pivot arm in meshing engagement with said drive gear; an elongated cam follower support arm having a center portion secured to said driven gear and first and second cam followers secured to opposite ends thereof; and a camming surface secured to said support means, at least one of said first and second cam followers engaging said cam surface and cooperating therewith to control rotational movement of said output shaft.
 10. Mechanical motion control apparatus as set forth in claim 9 wherein said camming surface provides a first portion cooperating with said cam followers to prevent rotation of said output shaft, a second portion cooperating with said cam followers to impart acceleration to said output shaft, and a third portion cooperating with said cam followers to impart a constant velocity motion to said output shaft.
 11. Mechanical motion control apparatus as set forth in claim 10 wherein only one of said cam followers engages said first portion of said camming surface.
 12. Mechanical motion control apparatus as set forth in claim 10 wherein both of said cam followers engage said third portion of said camming surface.
 13. Mechanical motion control apparatus as set forth in claim 12 wherein said first, second, and third portions of said camming surface provide a continuous curvilinear path.
 14. Mechanical motion control apparatus as set forth in claim 10 wherein said camming surface further includes a fourth portion cooperating with said cam followers to decelerate said output shaft and a fifth portion cooperating with said cam followers to prevent rotation of said output shaft.
 15. Mechanical motion control apparatus comprising:an input shaft; a drive means supported on said input shaft; a driven means supported in cooperating relationship with said drive means and adapted to be driven thereby; an elongated cam follower support arm secured to said driven means; a pair of cam followers secured to opposite ends of said support arm; and a stationary cam surface adapted to selectively engage one or both of said cam followers, said cam surface having a first portion cooperating with said cam followers to allow rotational movement of said driven means, a second portion cooperable with said cam followers to impart accelerating curvilinear motion to said driven means and a third portion cooperable with said cam followers to impart constant velocity curvilinear motion to said driven means.
 16. Mechanical motion control apparatus as set forth in claim 15 further including an output shaft operable connected to said driven means and wherein said input shaft rotates in a given direction from a time T_(s) to a time T_(f) and said output shaft is stationary until a time T_(o), T_(o) being between T_(s) and T_(f).
 17. Mechanical motion control apparatus as set forth in claim 16 wherein said output shaft is accelerated for a time T_(a) beginning at a time T_(o), T_(a) being less than T_(f) -T_(s).
 18. Mechanical motion control apparatus as set forth in claim 17 wherein said output shaft is decelerated at a time T_(d), T_(d) being subsequent to T_(o) +T_(a) and prior to T_(f).
 19. Mechanical motion control apparatus as set forth in claim 14 wherein said output shaft is rotated at a constant velocity for a period of time equal to T_(f) -T_(d) -(T_(a) +T_(o)). 